What the OBD-II code p0118 means

Fault code P0118 – a step-by-step guide to diagnosing and fixing it

The meaning of error code P0118 – Engine Coolant Temperature Sensor – High Input
P0118
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P0118: causes, symptoms and repairs

The meaning of fault code P0118

DTC P0118 is triggered by the control unit when the signal from the engine coolant temperature (ECT) sensor of the car indicates that the voltage input from the ECT circuit is too high. The sensor is a thermistor that is used to monitor temperature changes in the coolant system. The device’s electrical resistance fluctuates based on the temperature, causing changes in the voltage signal. The code is usually registered when the voltage is around 4.7 V - 4.91 V for a set amount of time, or the resistance is out of the normal range.

Common causes

  • A short in the voltage supply wire connected to the control module and ECT device. This can occur due to thermal or mechanical damage, such as a fraying or melted insulation sheath.
  • Oxidised electrical contacts, resulting in a bad connection. Oxidation can occur if the parts are exposed to dirt and moisture.
  • A failing thermistor, caused by engine components overheating.
  • A contaminated sensor. The cause of contamination is often a rusty coolant system, old antifreeze, or dirt contamination in the coolant expansion tank of the car.
  • Air pockets in the coolant lines. This slows down the temperature regulation process of the fluid.
  • Low coolant levels, affecting the sensor readings.
Possible symptoms of the P0118 code

  • Higher fuel consumption
  • Activation of the check engine light
  • Starting problems
  • Black smoke from the car's exhaust system parts
  • A rough idle
  • Engine misfires
  • Poor engine performance
Recommended repairs

  • Use an OBD2 scan tool to check for related DTCs, and read through the freeze frame data from when the DTC was set. This information should help you to identify the cause of the fault and obtain a proper diagnosis.
  • Inspect the wires and connectors for signs of damage or significant corrosion. You may need to disconnect the ECT sensor and check the circuit wires for wear or connection problems. Replace damaged components and remove traces of corrosion from the electrical contacts using a special cleaning agent.
  • Examine the cooling system to see whether the coolant levels are sufficient, there are air pockets, or the liquid is contaminated. It may be necessary to bleed the system and change the antifreeze for car.
  • You may need to measure the resistance of the ECT circuit using a multimeter. Check the vehicle manual for information on detaching the device before proceeding. If the circuit is functional, the reading should be around 2000 Ohms at room temperature. This value should decrease after applying heat (e.g. using a hairdryer). If the readings were abnormal, replace the sensor.
Frequently Asked Questions (FAQ)

What does “P0118” mean?


It means that the coolant temperature sensor circuit’s voltage is higher than it should be.

What are the causes of the P0118 code?


The most common causes of this DTC are electrical faults, including short or open circuits, corrosion and wire damage, and sensor failure.Other causes include contamination due to rust particles or dirt buildups in the system, and air pockets.

How serious is it?


We recommend that you refrain from using your car until it has been repaired. This ECT fault could cause the engine to go into emergency operation mode and potentially cause further damage to the unit.

How do I clear this DTC?


You can clear it by disconnecting the negative battery terminal to restart the onboard computer. If the check engine light is activated again, you should do another diagnostic scan. You will need to find the cause of the error and fix it before erasing the code from the computer’s memory archive.

Cars the fault code P0118 is most commonly found on

Fault code P0118 - Engine Coolant Temperature Sensor – High Input can occur with any car but is most often found on the following cars:

  • VW: Golf, Passat, Touran
  • Audi: A4
  • Honda: Civic, CRV
  • Peugeot: 308, 206, 207
  • Ford: Focus, Ka
  • Seat: Leon, Ibiza

If you get the code P0118 on your car, make sure that the diagnostics are carried out correctly and the error is still relevant. Check for symptoms associated with the problem and explore options for resolving it.

What to do if the fault code p 0118 appears

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